In recent years, more and more inter connected large-scale wind farms and ongoing deregulated environment take many challenges to transmission network expansion planning (TNEP). These challenges lie not only on more uncertainties of power flow in network but also on difficulty to compromise behalf of all new key stakeholders of power utilities. A novel algorithm is proposed in this paper. Firstly the power flow distribution and overload probability of network is calculated based on WTG output distribution and trade mechanism of power market. On this basis a new index which is introduced to evaluate the economic efficiency of all lines in candidate pool is proposed. Then low efficient lines are removed from the candidate pool step by step until optimum expansion scheme is obtained. Several experiments are carried out to demonstrate the performance of proposed algorithm on the modified Garver six-bus test system, then impacts of wind farm capacity and wind regime on TNEP are also discussed here.